1. Field of the Invention
The present invention relates to an imaging sheet roll containing a film coated with photosensitive microcapsules.
2. Description of the Prior Art
A printing method has been known to print an image of a color picture on a printing paper by utilizing photosensitive microcapsules. Such a conventional printing method will be first described with reference to FIGS. 1 to 3.
Referring initially to FIG. 1, a photosensitive film 1 is used which comprises a sheet or base 1a made of polyethylene terephthalate, polypropylene, polyamide or the like, and a microcapsule layer 2 which comprises a plurality of yellow, magenta and cyan microcapsules 2Y, 2M and 2C and is uniformly coated on the sheet or base 1a. Each of the yellow, magenta and cyan microcapsules 2Y, 2M and 2C has an outer shell made of a relatively soft material, such as, gelatin, polyvinyl alcohol, gum arabic or the like and a substance containing an optically-hardening composition sealed within each shell. This optically-hardening composition contains a pigment or a precursor thereof, such as photochromic dye, electrochromic dye, leuco dye and the like and an ethylene-based unsaturated compound or the like. When the optically-hardening composition is subject to irradiation with light of a particular wavelength, it is hardened, whereby the yellow, magenta and cyan microcapsules 2Y, 2M and 2C are selectively hardened. For example, irradiation with blue light hardens the yellow microcapsules 2Y containing the precursor of yellow pigment; irradiation with green light hardens the magenta microcapsules 2M containing the precursor of magenta pigment; and irradiation with red light hardens the cyan microcapsules 2C containing the precursor of cyan pigment, respectively.
As shown in FIG. 2, when the described microcapsule sheet 1 is irradiated with the light of a desired color picture, such light is analyzed into the three primary colors of red, green and blue, whereby the red light of the image, the green light of the image and the blue light of the image separately irradiate the photosensitive film whereby the microcapsules are respectively hardened by irradiation with beams of light of the corresponding colors for forming respective images as represented by hatched microcapsules 2a in FIG. 2. Then, the developing-process is performed as shown in FIG. 3.
In such developing process, a developing paper 3 is brought in contact with the microcapsule layer 2 of the film 1 that is already irradiated with the light images. The film 1 and the developing paper 3 are then pinched or pressed between rollers 4a and 4b. Then, the pressure breaks the outer shells of the yellow, magenta and cyan microcapsules 2Y, 2M and 2C that are not hardened by the irradiation of light having a corresponding wavelength, thus transferring the substances containing precursors of pigments from within the microcapsules to the surface of the developing paper 3. When the precursors of pigments of the respective colors are transferred to this developing paper 3, the surface of the developing paper 3 is developed with the corresponding colors (yellow, magenta and cyan). The mixing of these three colors presents a color picture which is developed (or printed) on the developing paper 3.
In the prior art, the long photosensitive film 1 is wound in the form of a roll around a spool located rotatably within a cassette casing that is arranged to shield the film from light coming from the outside. In use, this long photosensitive film 1 is loaded on a cassette loading portion of a printer while the film is kept within the cassette casing.
This kind of conventional photosensitive film cassette 7 is shown in FIG. 4 to comprise a cassette casing 5 of substantially cylindrical configuration, a spool 6 rotatably provided within the cassette casing 5 and around which the long photosensitive film 1 is wound, a film outlet 8 of substantially slit configuration extending through the outer peripheral portion of the cassette casing 5 along the axial direction of the cassette casing 5 and pads 9, 9 attached to the two inner side walls of the film outlet 8 along the longitudinal direction of the film outlet 8 to shield the film from light from the outside. The free end portion of the photosensitive film 1 is widthdrawn through the spacing between the opposing surfaces of the light-shielding pads 9, 9 and advanced from the film outlet 8 to the outside of the cassette casing 5. If the photosensitive film 1 is pinched firmly between the pads 9, 9 so that the photosensitive film 1 can be perfectly protected from being irradiated with light at the film outlet 8, the photosensitive film 1 shown in FIGS. 1 to 3 is inevitably rubbed by the pads 9, 9 with a very large friction force during its feeding from the cassette casing 5 with the result that the photosensitive film 1 is scratched and damaged by the pads 9 and 9, and at least some of the microcapsules are broken.
On the other hand, if the pads 9, 9 are arranged to contact the phtosensitive film 1 with only a small pressure in order to protect the photosensitive film 1 from being damaged as much as possible, the light-shielding effect at the film outlet 8 is lowered.
To solve such a problem the assignee of the present application has previously prosposed a photosensitive film cassette as shown in FIG. 5 (and as disclosed in Japanese Patent Application No. 62-140913). In FIG. 5 parts corresponding to those of FIG. 4 are identified by the same references and will not be again described in detail.
FIG. 5 shows the photosensitive film cassette 7 within which the photosensitive film 1 is wound around the spool 6 in the form of a roll of film. The film outlet 8 is formed through the cassette casing 5 to permit the photosensitive film 1 to be withdrawn therethrough. Further, the photosensitive film cassette 7 is provided with a light-shielding member 10 which is pivotably supported by the cassette casing 5 for movement toward and away from one inner side surface of the film outlet 8 to thereby close the film outlet 8, spring biasing means (not shown, are provided for always spring-biasing the light-shielding member 10 such that the light-shielding member 10 closes the film outlet 8. An actuating portion (not shown) on the member 10 is pressed by a pressing portion of a predetermined cassette loading portion so as to move the light-shielding member 10 away from the inner side surface of the film outlet 8 when the photosensitive film cassette 7 is loaded on the cassette loading portion. Reference numerals 11, 11 designate flanges that are engaged with both ends of the cassette casing 5 to rotatably support the spool 6.
When the photosensitive film cassette 7 is not loaded on the predetermined cassette loading portion, the light-shielding member 10 resiliently contacts with the one inner side surface of the film outlet 8 with the photosensitive film 1 being gripped therebetween so that light-shielding of the photosensitive film 1 at the film outlet 8 can be positively effected. Also, this light-shielding state can be maintained stably. Further, when the photosensitive film cassette 7 is loaded on the predetermined cassette loading portion, the light-shielding member 10 is spaced apart from the inner side surface of the film outlet 8 so that the photosensitive film 1 can be freely advanced through such outlet and is prevented from being damaged by the light-shielding member 10 in its advancement from the cassette casing 5. In addition, when the photosensitive film cassette 7 is loaded on the film cassette loading portion, the light-shielding member 10 is automatically spaced apart from the inner side surface of the film outlet 8 without the need for any special operation to be perfomed by the user.
However, with the arrangement shown in FIGS. 4 and 5, the photosensitive film cassette 7 needs not only the cassette casing 5 but also the light-shielding pads 9, 9 or the light-shielding member 10, respectively for shielding the light. Moreover, the photosensitive film cassette 7 needs a relatively complex built-in mechanism when the light-shielding member 10 is employed. This increases the cost of the photosensitive film cassette 7 which is thereby unsuited for use as product on the market.